The invention relates to the monitoring of an effluent from a process chamber.
In the processing of substrates, semiconductor, dielectric, and conductor materials, such as for example, polysilicon, silicon dioxide, aluminum and/or tungsten silicide, are formed on a substrate by chemical vapor deposition (CVD), physical vapor deposition (PVD), oxidation and nitridation processes. For example, in CVD processes, a reactive gas is used to deposit material on the substrate, and in PVD processes, a target is sputtered to deposit material on the substrate. In oxidation and nitridation processes, an oxide or nitride material, typically silicon dioxide or silicon nitride, respectively, is formed on the substrate by exposing the substrate to a suitable gaseous environment. In conventional etching processes, a patterned mask of photoresist or oxide hard mask is formed on the substrate by lithographic methods, and the exposed portions of the substrate are etched typically by energized gas to form patterns of gates, vias, contact holes or interconnect lines. During such processes, process residues often deposit on the walls, components and other surfaces in the chamber. The process residues are undesirable because they can flake off and contaminate the substrate on which they deposit. In a conventional process, the etchant residue is periodically cleaned off the surfaces in the chamber. For example, in one method, after processing a batch of substrates, a dry-cleaning process is used to clean the chamber surfaces with an energized cleaning gas. In another method, the cleaning gas is added to the etchant gas, and the resultant gas composition is energized to both etch the substrate and clean the surfaces in the chamber.
In such processes, it is often desirable to stop processing after a predetermined period, at an end of a processing stage, or at a process endpoint. For example, when performing a chamber cleaning process, it may be desirable to stop the cleaning process when substantially all, or a portion, of the process residue deposited on the chamber surfaces have been cleaned, i.e., they have been removed or prevented from being deposited. Excessive cleaning may shorten the lifetime of chamber components or otherwise degrade subsequent substrate processing. However, when the thickness of the process residue varies in the processing of one substrate or another, it may be difficult to uniformly clean the chamber in each cleaning cycle. Also, the efficiency of the cleaning process at different locations across the chamber may depend upon plasma density and distribution. Accordingly, it may be difficult to determine completion of the cleaning process.
Thus, it is desirable to stop processing after a predetermined period or to determine a process endpoint, such as an endpoint of a chamber cleaning process. It is also desirable to clean chamber walls and surfaces without erosion of chamber surfaces.
The present invention satisfies these needs. In one version, the invention comprises an effluent monitoring apparatus comprising a cell adapted to receive an effluent, a gas energizer capable of energizing the effluent in the cell thereby emitting a radiation, a radiation permeable window that is spaced apart or recessed from a wall of the cell by a distance d that is sufficiently high to reduce a deposition of process residue from the energized gas on the window, and a detector to detect the radiation. The window may be located in a port which has an aspect ratio that is sufficiently high to reduce the deposition of effluent residue from the energized gas on the window.
In another aspect, the invention comprises a method of monitoring a composition of an effluent from a process chamber, the method comprising introducing the effluent into an effluent energizing cell, energizing the effluent in the cell, maintaining a radiation permeable window spaced apart from a wall of the cell at a distance d that is sufficiently large to reduce the deposition of effluent residue on the window, and detecting a radiation emanating from the energized gas and passing through the window.
In yet another aspect, the invention comprises a chamber cleaning apparatus comprising a chamber comprising a support capable of supporting a substrate during processing, a gas supply to provide a cleaning gas to the chamber, a gas energizer to energize the cleaning gas, and an exhaust to remove spent cleaning gas from the chamber; and a process monitoring system comprising a gas energizing cell in the exhaust to receive spent cleaning gas, a gas energizer capable of energizing the gas in the cell, a window assembly comprising a radiation permeable portion that is spaced apart from the cell wall at a distance that is sufficiently large to reduce the deposition of effluent residue on the radiation permeable portion, and a detector to detect a radiation emanating from the energized gas.
In a further aspect, the invention comprises an effluent monitoring apparatus comprising a cell to receive effluent, one or more electrodes in the cell that are chargeable to form a plasma from the effluent in the cell, a detector assembly comprising a radiation permeable window, and a sensor behind the window to detect radiation emanating from the plasma, and optional optics, wherein the detector assembly is set to selectively receive radiation originating from the front of an electrode in the cell.
In another aspect, the invention comprises a method of monitoring an effluent, the method comprising introducing an effluent into a cell, applying a bias voltage to one or more electrodes in the cell to form a plasma of the effluent, providing a radiation permeable window in the cell, and detecting radiation emanating from the front of an electrode.
In yet another aspect, the invention comprises a chamber cleaning apparatus comprising a chamber comprising a support capable of supporting a substrate during processing, a gas supply to provide a cleaning gas to the chamber, a first gas energizer to energize the cleaning gas, and an exhaust to exhaust cleaning gas; and a process monitoring system comprising a cell adapted to receive cleaning gas, electrodes that may be biased to energize the cleaning gas in the cell, a detector assembly comprising a radiation permeable window and a detector to detect radiation emanating from the energized cleaning gas in front of the electrode.